System for establishing ligament graft orientation and isometry

• US 4,712,542 A
• Filed: 06/30/1986
• Issued: 12/15/1987
• Est. Priority Date: 06/30/1986
• Status: Expired due to Term

• Current Assignee: Medmetric Corporation
• Original Assignee: Medmetric Corporation
• Inventors: Daniel, Dale M., Watkins, Kay R.
• Primary Examiner(s): Rosenbaum, C. Fred
• Assistant Examiner(s): Shedd, C. W.
• Application Number:
  US06/880,055
• Time in Patent Office: 533 Days
• Field of Search: 128/92 VD, 128/92 V, 128/92 R, 128/92 VL, 128/92 VK, 128/303 R, 623/13, 623/20
• US Class Current: 606/96
• CPC Class Codes: A61F 2/0805 Implements for inserting tendons or ligaments

Abstract

A method and instrument for skeletal referenced isometric positioning and tensioning of a ligament graft, particularly during knee surgery involving the anterior cruciate and the posterior cruciate ligaments. The graft is extended from one fixation site and attached to a sled slidably carried by a frame which is skeletally mounted to the other fixation site. A thumb nut and lead screw assembly on the skeletally fixed frame is operative to compress a spring in the sled and move the sled in a direction effective to tension the graft. Isometry is achieved when the relative positions of the frame and sled indicate constant graft tension and displacement through the entire range of passive knee flexion. The sled can be fixed relative to the frame for evaluation of joint laxity.

Claims

1. A method for establishing skeletal referenced isometric positioning and tensioning of a ligament graft between fixation sites on a pair of articulated bones, said method comprising the steps of:

establishing the locations of said fixation sites;

drilling openings in said bones between said fixation sites;

skeletally fixing a first portion of an instrument adjacent one of said fixation sites;

disposing a tension element through said openings, temporarily fixing one end of said element at the other of said fixation sites, and temporarily fixing the other end of said element to a second portion of said instrument which is movable relative to said first portion for displacement of said element.

determining the amount of the movement of said second portion relative to said first portion, and the amount of said bias to establish the amount of said displacement and tension during flexion of said bones and, if necessary, reestablishing said fixation sites and openings until said amount of said displacement and said tension satisfy predetermined criteria;

drilling larger graft openings in said bones between the established fixation sites;

repeating the foregoing skeletally fixing, disposing and determining steps relative to said graft; and

fixing said graft to the established fixation sites.

2. A method for establishing skeletal referenced isometric positioning and tensioning of a cruciate knee ligament graft between femoral and tibial fixation sites, said method comprising the steps of:

approximating the location of said fixation sites;

drilling openings in the femur and tibia between said fixation sites;

skeletally fixing a first portion of an instrument adjacent one of said fixation sites;

disposing a tension element through said openings, temporarily fixing one end of said element at the other of said fixation sites, and temporarily fixing the other end of said element to a second portion of said instrument which is movable relative to said first portion for displacement of said element.

moving said second portion relative to said first portion against a bias to develop tension in said element;

determining the amount of the movement of said second portion relative to said first portion, and the amount of said bias to establish the amount of said displacement and tension during knee flexion and, if necessary, reestablishing said fixation sites and openings until said amount of said displacement and said tension remain substantially constant throughout said flexion;

drilling larger graft openings in said femur and tibia between the established fixation sites;

repeating the foregoing skeletally fixing, disposing and determining steps relative to said graft; and

fixing said graft to the established femoral and tibial fixation sites.

3. An instrument for use in establishing skeletal referenced isometric positioning and tensioning of a ligament graft which passes between fixation sites on a pair of articulated bones, said instrument comprising:

an elongated frame having nose means operative to effect skeletal engagement of said frame adjacent one of the fixation sites, said frame further having elongated sled guide means;

a sled longitudinally slidable upon said sled guide means;

graft retaining means carried by said sled and operative to hold and fix, relative to said sled, the free end of a graft passing from the other of said fixation sites;

indicating means carried by said frame and said sled and cooperative to indicate the longitudinal position of said sled relative to said frame thereby to indicate any displacement of the graft;

bias development means carried by said frame and said sled and alternately operative to develop an increasing bias upon said sled to move said sled and increase the tension in the graft, or to develop a decreasing bias upon said sled to move said sled and decrease the tension in the graft; and

sled fixing means carried by said frame and operative to fix said sled against movement relative to said frame.

4. An instrument according to claim 3 wherein said graft passes through drill holes in said bones, and said nose means comprises a tubuar nose through which said graft is movable, and wherein said tubular nose is adapted to seat within the drill hole adjacent said one of said fixation sites to effect said skeletal engagement.

5. An instrument according to claim 4 wherein said nose is laterally open and separably mounted to said frame whereby said nose is separable from said graft and from said frame subsequent fixation of the graft to said one of said fixation sites.

6. An instrument according to claim 3 wherein said graft passes through drill holes in said bones, and said nose means comprises a tubular nose through which said graft is movable, and wherein said tubular nose mounts a bracket adapted to receive a cortical screw to effect said skeletal engagement.

7. An instrument according to claim 3 wherein said sled includes a central cavity, and wherein said bias development means comprises:

a threaded nut rotatably carried by said frame;

a lead screw threadably engaged by said nut and terminating in an abutment element located in said cavity; and

a compression spring having its opposite ends engaged upon said abutment element and said sled, respectively.

8. An instrument according to claim 7 wherein said sled carries force indicia, and said abutment element constitutes an indicator movable relative to said force indicia to establish the level of said tension in the graft.

9. An instrument according to claim 3 wherein said indicating means comprises indicia on said frame and said sled to indicate said longitudinal position of said sled relative to said frame.

10. An instrument according to claim 3 wherein said indicating means comprises:

a rack on said sled; and

a gear carried by said frame, meshed with said rack and having a dial face, said dial face and said frame including indicia cooperative to indicate said longitudinal position of said sled relative to said frame.

11. A method for establishing skeletal referenced isometric positioning and tensioning of an anterior cruciate knee ligament graft between femoral and tibial fixation sites, said method comprising the steps of:

approximating the location of said fixation sites;

drilling suture openings in the femur and tibia between said fixation sites;

inserting into the tibial suture opening a nose portion of an instrument frame to skeletally fix said frame adjacent said tibial fixation site;

disposing a suture through said openings and said nose portion, temporarily fixing one end of said suture at said femoral fixation site, and temporarily fixing the other end of said suture to a sled which is movable on said frame for longitudinally displacing said suture, the movement of said sled relative to said frame being through a bias means to develop a determinable tension in said suture;

determining the amount of said displacement and tension during knee flexion and, if necessary, reestablishing said fixation sites and suture openings until said amount of said displacement and said tension remain substantially constant throughout said flexion;

enlarging said suture openings between the finally established fixation sites to form graft openings;

repeating the foregoing inserting, disposing and determining steps relative to said graft;

fixing said graft to the established femoral and tibial fixation sites; and

separating said nose portion from said graft.

12. An instrument for use in establishing skeletal referenced isometric positioning and tensioning of a cruciate knee ligament graft which passes through holes extending between femoral and tibial fixation sites, said instrument comprising:

an elongated frame having a nose portion receivable in the hole adjacent said tibial fixation site to skeletally fix said frame adjacent said tibial fixation site, said frame further having elongated sled guide means;

a threaded nut rotatably carried by said frame;

a lead screw threadably engaged by said nut and terminating in an abutment element;

a sled longitudinally slidable upon said sled guide means and relative to said lead screw, and including a central cavity receiving said abutment element, said sled including force indicia cooperative with said abutment element to indicate the longitudinal position of said abutment element relative to said sled;

graft retaining means carried by said sled and operative to hold and fix, relative to said sled, the free end of a graft passing from said femoral fixation site and through said distal nose portion;

displacement indicating means carried by said frame and said sled and cooperative to indicate the longitudinal position of said sled relative to said frame thereby to indicate any displacement of the graft;

a compression spring carried by and having its opposite ends engaged upon said abutment element and said sled, respectively, said nut being operative in one direction to develop an increasing bias upon said sled to move said sled and increase the tension in the graft, and operative in the opposite direction to develop a decreasing bias upon said sled to move said sled and decrease the tension in the graft, the relative position of said abutment element and said force indicia indicating the amount of tension in the graft; and

sled fixing means carried by said frame and operative to fix said sled against movement relative to said frame.

13. An instrument according to claim 12 wherein said nose portion is laterally open and separably mounted to said frame whereby said nose is laterally separable from said graft and from said frame subsequent fixation of the graft to said tibial fixation site.

14. An instrument according to claim 12 wherein said displacement indicating means comprises indicia on said frame and said sled to indicate said longitudinal position of said sled relative to said frame.

15. An instrument according to claim 12 wherein said displacement indicating means comprises:

a rack on said sled; and

a gear carried by said frame, meshed with said rack and having a dial face, said dial face and said frame including indicia cooperative to indicate said longitudinal position of said sled relative to said frame.